Lightning Strikes and Attribution of Climatic Change

TL;DR

This paper discusses methods for attributing changes in lightning strike frequency to climate change, addressing statistical and data challenges to improve attribution accuracy and understanding of climate impacts.

Contribution

It introduces two schemes for attributing lightning strike changes to climate change, accounting for fluctuations and confounding variables, and highlights data-driven attribution challenges.

Findings

Attribution fractions differ from epidemiological studies.

Temperature standardization helps account for cyclical influences.

Climate change may alter the relationship between temperature and strike frequency.

Abstract

Using lightning strikes as an example, two possible schemes are discussed for the attribution of changes in event frequency to climate change, and estimating the cost associated with them. The schemes determine the fraction of events that should be attributed to climatic change, and the fraction that should be attributed to natural chance. They both allow for the expected increase in claims and the fluctuations about this expected value. Importantly, the attribution fraction proposed in the second of these schemes is necessarily different to that found in epidemiological studies. This ensures that the statistically expected fraction of attributed claims is correctly equal to the expected increase in claims. The analysis of lightning data highlights two particular difficulties with data-driven, as opposed to modeled, attribution studies. The first is the possibility of unknown "confounding" variables that can influence the strike frequency. This is partly accounted for here by considering the influence of temperature changes within a given month, so as to standardise the data to allow for cyclical climatic influences. The second is the possibility suggested by the data presented here, that climate change may lead to qualitatively different climate patterns, with a different relationship between e.g. strike frequency and temperature.